Max Planck Institute for Astronomy | 2019 Jan 24
Using the ALMA observatory in Chile, a group of astronomers led by MPIA’s Henrik Beuther has made the most detailed observation yet of the way that a giant gas cloud fragments into dense cores, which then act as the birthplaces of stars. The astronomers found that the mechanisms for fragmentation are fairly straightforward, resulting from the combination of the cloud’s pressure and gravity. More complex features, such as magnetic lines or turbulence, play a smaller role than previously thought.
Stars are born when giant clouds of gas and dust collapse. Whenever one of the collapsing regions becomes hot and dense enough for nuclear fusion to set in, a star is born. For massive stars, i.e. those stars that exhibit more than eight times the mass of the Sun, that is only part of the picture, though. The biggest stars in the Universe are not born singly. They are born from massive clouds of molecular gas, which then form a cascade of fragments, with many of the fragments giving birth to a star.
Astronomers have long wondered whether this fragmentation-mode of forming stars requires different physical mechanisms than for lower-mass stars. Proposals include turbulent gas motion, which could destabilize a region and lead to quicker collapse, or magnetic fields that could stabilize and thus delay collapse.
The different mechanisms should leave tell-tale traces in regions where multiple stars are forming. The collapse that leads to the formation of high-mass stars takes place on a hierarchy of different levels. On the largest scales, star formation involves giant molecular clouds, which consist mostly of hydrogen gas and can reach sizes between a few dozen and more than a hundred light-years across. Within those clouds are slightly denser clumps, typically a few light-years across. Each clump contains one or more dense cores, less than a fifth of a light-year in diameter. Within each core, collapse leads to the formation of either a single star or multiple stars. Together, the stars produced in the cores of a single clump will form a star cluster. ...
High-Mass Star Formation at Sub-50 AU Scales ~ H. Beuther et al
- Astronomy & Astrophysics 621:A122 (Jan 2019) DOI: 10.1051/0004-6361/201834064
arXiv.org > astro-ph > arXiv:1811.10245 > 26 Nov 2018